class Phone:
    __is_5g_enable = None

    def __init__(self):
        import random
        randint = random.randint(0, 1)
        self.__is_5g_enable = randint == 1

    def __check_5g(self):
        if self.__is_5g_enable:
            print('5g开启')
        else:
            print('5g关闭，使用4g网络')

    def call_by_5g(self):
        self.__check_5g()
        print('正在通话中...')


phone = Phone()
phone.call_by_5g()
